The union claimed the Government had worsened its offer on pensions and retirement age to firefighters ahead of the latest strike.

Officials said Fire Minister Brandon Lewis wrote to the FBU on Friday afternoon, three hours before the last stoppage, saying his last offer “was conditional on acceptance” and that it was being withdrawn.

Some brigades, including London, have hired contractors to provide cover, while others are relying on part-time and retained staff.

The dispute is over pension age changes which will see fireighters’ retirement age increased from 55 to 60.

The union fears firefighters will be made redundant if they fail fitness tests and are unable to find other work in the fire service.

No action is being taken in Scotland while talks between the union and the Scottish government continue.

FBU general secretary Matt Wrack said: “By worsening the proposals for firefighters’ pensions, the Government has now put a further obstacle in the way of negotiations, but after two years of talks the Fire Brigades Union remain committed to a resolution.

“No firefighter wanted a strike, but we must defend the fire service, public safety and our pensions. The situation has now been exacerbated by ill-informed interventions by Chief Fire Officers which completely contradict Government claims that nobody will be sacked.

“In a bizarre twist Chief Officers are saying that firefighters will have a ‘choice’ of being sacked. Firefighters will wonder what planet these very highly paid Chief Officers are living on.

“We can still get sorted this mess out if the Government recognises our concerns and takes account of the real evidence we have given them.”

Mr Lewis said: “This strike action by the FBU is completely unnecessary and does nothing but damage the good reputation firefighters have with the public.

“We offered firefighters similar fitness principles to those the FBU accepted in Scotland. The FBU should reconsider their decision to strike – announced just four days into discussions – and work for a resolution to this dispute.

“The public will be baffled by the FBU’s course of action when they hear that the deal being offered to firefighters gives them one of the most generous pension schemes in all the public sector.

“A firefighter who earns £29,000, and retires after a full career aged 60, will get a £19,000 a year pension, rising to £26,000 with the state pension.

“An equivalent private pension pot would be worth over half a million pounds and require firefighters to contribute twice as much.”